Over-the-top (OTT) delivery can be defined as the delivery of content, e.g. voice and or video, over an access network without the access network provider being involved in the control or distribution of the content itself. Today OTT services are delivered as normal best effort (BE) traffic. However, in some cases the OTT applications require specific treatment in order to obtain a satisfactory experience at the receiver side, often referred as Quality of Experience (QoE). This is particularly true in the case of cellular access networks.
One important application example is that of instantaneous video delivery. Typical video applications are designed for the Internet and a way to address the problems resulting from network congestion is to temporarily stop the rendering of new video-data on a user terminal's display, and instead present a “frozen-image”. A spinning symbol may appear on the display to inform the user that the player is waiting for new data and until the size of the buffered video reaches some pre-configured threshold. The player may attempt to adapt to the congestion situation by increasing the pre-configured threshold.
New deployments of video streaming applications, e.g., chunk-based HTTP-streaming, assume that the client or server adjusts the data volume based on the measured TCP-throughput. The lower the data volume, the lower the experienced video quality. However, frozen images can be eliminated if the TCP-throughput is above a certain lower bound. It is noted that such applications may deliver a significantly reduced QoE (as compared with non-chunk based mechanisms) when the resources are below some minimal bandwidth threshold. When a chunk has been downloaded, a video may start to play but then playout stops before the next chunk is present in the buffer. This means that the occurrence of frozen image will be frequent compared with a progressive download of the content.